1. Field of the Invention
The present invention relates to an ophthalmologic photographing apparatus used in an ophthalmologic doctor's office, a group medical examination, or the like for photographing a subject's eye and performing image processing on a photographed fundus image.
2. Description of the Related Art
A fundus camera for photographing a fundus of a subject's eye has been known as an ophthalmologic photographing apparatus. Particularly, a fundus camera has been known, which has a plurality of photographing modes, such as a color photographing mode, a visible fluorescent photographing mode (fluorescent angiography (FAG) photographing mode) and an infrared fluorescent photographing mode (indocyanin green (ICG) photographing mode), in order to observe a subject's eye and to perform photographing according to an examination purpose.
Japanese Patent Laid-Open No. 2001-245851 discusses an apparatus that automatically sets parameters, such as again, a gamma value, or a color temperature, for a television camera mounted in an ophthalmologic photographing apparatus according to the plurality of photographing modes. Japanese Patent Laid-Open No. 2004-187811 discusses an apparatus that performs image processing with an optimum processing parameter corresponding to each of the plurality of photographing modes.
When visible fluorescent photographing of a fundus of a subject's eye is performed, an original image obtained by the visible fluorescent photographing is a greenish color image. However, for easier image-interpretation, the color image is converted into a monochrome image. In addition, gradation conversion processing, such as gamma characteristic adjustment or contrast processing, is performed as the image processing using the above optimum processing parameters. Similarly, when infrared fluorescent photographing of a fundus of a subject's eye is performed, generally, diagnosis is made using an image that is obtained by performing gamma characteristic adjustment, contrast processing, or the like.
Conventional ophthalmologic photographing apparatuses having a plurality of photographing modes have employed the following two methods.
(1) A method of performing, just after an image of a subject's eye is photographed, image processing on a raw captured image of the subject's eye and then conducting image-interpretation of a compressed image.
(2) A method of storing the entire original captured image of a subject's eye and then performing image-interpretation of the stored original image.
However, when image-interpretation is performed using the method (1), hue information, and gradation information representing density levels or the like are insufficient. Thus, it is difficult to observe a lesion. There is a risk that oversight of a lesion may occur at worst. On the other hand, when image-interpretation is performed by the method (2), gradation information is not insufficient. However, due to a recent high increase in resolution of image sensors, an amount of image data representing a photographed image of a subject's eye has become enormous, with result of reduction in processing speed of ophthalmologic photographing apparatuses and increase in recorded data. Accordingly, loads of ophthalmologic photographing apparatuses increase. Thus, usability thereof becomes poor.